Hey m21man,
You can UnPBO the Resistance campaign and take a look at the tenth cutscene (x10_something if I remember well), and also have a look at uiox' amazing
tut'.
To attach a particle to the roof of a vehicle, you just need to define the initial relative position of the particle (say, [0,0,1.5]) : the last argument will then be the name of the vehicle itself.
Drop [blabla, [0,0,1.5], blabla, "","",truck]
(I don't have my ComRef here, can't be more specific).
Ig.